Bug Description

I use Ubuntu 9.10 with Dutch localization. When I install Mozilla Thunderbird from the repositories, Thunderbird isn't being localized automatically: the interface is 100 % English.

I have to run System - Administration - Language Support to install the missing Thunderbird language packs as yet. This step shouldn't be necessary: when I install Thunderbird in a localized Ubuntu 9.10, the necessary language packs should come with it automatically.

We can only fix this in software-center.
In language-selector, we have a python class called CheckLanguageSupport(), which takes two arguments, datadir="/usr/share/language-selector" and cache=, where cache is the already opened package cache in use.
Then, before installing the selected packges and their dependencies, software-center would need to call getMissingPackages(packages=[list of packages which are going to be installed]). This will return a list of translation or writing aids packages, which have not been installed yet, but where the base application is marked for installation or is already installed on the system.
Finally, software-center should depend on language-selector-common.

Indeed, I added synaptic by mistake when i tried to add thunderbird-locales. As I could not find thunderbird-locales, I left thunderbird.
If someone knows how to change it to thunderbird-locales (as it was done on bug #280651), please do it :)

I realized my problem: while installing ubuntu, I didn't have an internet connection to load the german language packages, because my dsl-connection was not configured. As I read the bug description again, I went to System - Administration - Language Support and installed the missing language packs. Now everything is ok.